Valence space techniques and QRPA vibrational mass parameters

I Deloncle,F Lechaftois,S Péru

doi:10.1088/1742-6596/724/1/012012

Abstract

The vibrational mass parameters entering the quadrupolar 5DCH Hamiltonian are commonly obtained neglecting beyond mean-field correlations and the dynamical mean-field rearrangement. The Quasiparticle Random Phase Approximation (QRPA) framework would allow to avoid these disadvantages [1], if the computation time, when using density dependent force, was not prohibitive. Here, a significant time reduction is obtained by applying valence space (VS) techniques (energy cut-off and inert core) in QRPA calculations. The VS techniques allow to probe the physical content of the mass parameter. The QRPA mass parameter exhibit robustness toward VS limitations contrarily to the intrinsic QRPA outputs, that show deceptive appearance when an inert core is used. Excited states energy, and associated transition probabilities, should not be considered for optimizing the valence space limits.

Highlights

In the 5DCH theory the Bohr Hamiltonian is built and solved microscopically, without any free parameter
The 110−144Sn isotopes have a minimum of HFB energy at zero deformation, where the Quasiparticle Random Phase Approximation (QRPA) and the mass parameter calculations will be performed
It allows to decorrelate the notion of valence space from deformation

Summary

Introduction

In the 5DCH theory the Bohr Hamiltonian is built and solved microscopically, without any free parameter. Lechaftois, S.Peru but not in practice due to the prohibitive QRPA time consumption, in particular when using a density-dependent force On another hand, the strong variations with the deformation of the vibrational mass parameters [5, 6] impose to compute them for a large amount of β,γ values. We explore its consequence on mass parameter Another way of limiting the valence space is used in standard shell model: the introduction of an inert core that put aside the lowest single-particle levels. We apply this technique for the first time in QRPA calculations. It is compared to the one observed for the built-in QRPA outputs, namely phonon energies and reduced transition probabilities

Form TDHFB to Inglis-Belyaev

Results

Mass parameter with 2qp energy cut-off

Mass parameter with inert core

QRPA outputs with inert core